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biology- core components > cell membranes > Flashcards

cell membranes Flashcards

1
Q

what are the roles of the cell plasma membrane

A
  • seperates the cell contents from the outside environment
  • regulates the transport of nutrients into and out of the cells- selectively/partially permeable
  • recepetor sites- eg hormones bind to target cells which have correct receptor sites
  • recognition- cell membranes have built in protein-based antigens which enable cells to recognise other and to trigger an immune response
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2
Q

what are the roles of the internal membrane

A
  • seperate cell components from cytoplasm
  • hold the components of some metabolic pathways in place
  • chemical reactions take place on membranes
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3
Q

what is the fluid-mosaic model

A

singer and nicholson (1972)- proposed a model of how the components in the membarne are arranged

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4
Q

why is the model called fluid

A

the phosphate molecules move around each other within a layer realtive to one another

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5
Q

why is the model called mosaic

A

proteins emmbedded between the phospholipids vary in shape, size and pattern

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6
Q

what are the components of a cell membrane

A
  • phosphate bilayer
  • proteins (intrinsic and extrinsic)
  • chlorestrol
  • glycoproteins and glycolipids
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7
Q

whats the difference between intrinsic and extrinsic proteins

A

intrinsic span the bilayer whereas extrinsic are only on 1 side of bilayer

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8
Q

whats the components of the phospholipid bilayer

A

hydrophilic heads pointing outwards (interact with water)
hydrophobic tails point towards each other

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9
Q

what are characteristics of extrinsic proteins

A
  • on surface of the bilayer
  • provide structural support
  • form recognistion sites by identifying cells
  • form receptor sites for horn attachments
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10
Q

what are characteristics of intrinsic proteins

A
  • extended across the bilayer
  • provide structural support
  • some are carrier proteins- active transportor diffusion of water- soluble substances and large polar molecules
  • some are channel proteins
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11
Q

whats the function of cholestrol in the membrane

A

provides the membrane with stability and rigidity by fitting between the fatty acid tails

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12
Q

whats the function of glycoproteins and glycolipids

A

for cell to cell communication, cell to cell recognition, hormone reception

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13
Q

what makes up a glycoprotein

A

protein and carbohydrate

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14
Q

what makes up glycolipid

A

phosopholipid and carbohydrate

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15
Q

what is glycocalyx

A

the carbohydrate layer around the membrane

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16
Q

what is the membrane a barrier to

A
  • larger polar molecules
  • water-soluble molecules
  • ions
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17
Q

what is the membrane freely permeable to

A
  • lipid-soluble substances
  • non-polar molecules
  • very small polar molecules
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18
Q

what happens when membrane are heated

A

as the temp increases, the molecules that make up the membrane gain kinetic energy causing the membrane to become more fluid and therefore more permeable for pigments and solutes

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19
Q

what are the different methods of passive transport

A
  • diffusion
  • facilitated diffusion
  • osmosis
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20
Q

what is diffusion

A

a passive movement of molecules from a region of high conc to low conc gradient down a conc gradient

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21
Q

when does diffusion occur

A
  • there is a conc gradient
  • molecules have kinetic energy
  • no ATP energy required
  • no specific proteins required
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22
Q

how does temperature effect diffusion

A

increasing temp increases kinetic energy and the rate of random movement so the diffusion rate increases

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23
Q

how does concentration gradient effect diffusion

A

having more molecules on one side of the membrane increases diffusion rate by increasing conc gradient

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24
Q

how does surface area effect diffussion

A

the greater the rate surface area the greater the rate of diffusion

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25
Q

whats the equation for rate of diffusion

A

rate of diffusion =
(surface area x difference in conc)/ length of diffusion pathway

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26
Q

how does membrane thickness effect diffusion

A

the thicker the membrane the slower the rate of diffusion

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27
Q

how does diffusion distance effect diffusion

A

the shorter distance, the greater the rate of diffusion

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28
Q

how does the size of moelcules effect diffusion

A

smaller molecules diffuse mre quickly

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29
Q

how does lipid solubility effect diffusion

A

the more lipid soluble the molecule, the faster the rate of diffusion

30
Q

what is facilitated diffusion

A

passive transfer of molecules or ions down a conc gradient, across a membrane by protein carrier molecules in the membrane

31
Q

what are the characteristics of hydrophilic channel proteins

A
  • molecules with pores lined with polar groups
  • each protein is specific and will only allow one type of ion through due to specific shape
  • channel can be gated so they only open/close in specific conditions
32
Q

what are the characteristics of carrier proteins

A
  • allow specific large plant molecules to pass through the membrane
  • a particular molecule will attach to the protein at its binding site and cause the protein to change shape and releasing the molecule through the membrane
33
Q

what are some faciliated diffusion facts

A
  • there is a conc gradient
  • molecules have kinetic energy will be in a state of random movement
  • no ATP energy needed
  • protein hydrophillic channels/ carries are present
34
Q

what are the types of active transport

A
  • via carrier proteins
  • bulk transport
35
Q

what are characteristics of active transport via carrier proteins

A
  • movement of ions and other moelcules across the membrane via carrier proteins
  • substances can be moved from a low conc to a high conc gradient against a conc gradient. it does require ATP
36
Q

what is the mechanism of active uptake

A
  1. the molecule or ion combines with a specific carrier protein on the outside of the membrane
  2. ATP transfers a phosphate group to the carrier protein on the inside of the membrane
  3. the carrier proteins cahnges shape and carries the molecule or ion across the membranes to the inside of the cell
  4. the molecule/ion is released into the cytoplasm
  5. the phosphate ion is released from the carrier molecule back to the cytoplasm and recombines with ADP to form ATP
37
Q

what are facts about active transport

A
  • intrinsic protein carriers are present
  • if a respiratory inhibitor is present (cyanide) active transport will be reduced or wont take place
38
Q

examples of processes involving active transport

A
  • protein synthesis
  • muscle contraction
  • nerve impulse transmission
  • absoprtion of mineral salt by plant roots
  • reabsorption of glucose in kidneys
39
Q

what is bulk transport

A

bulk transport of substances into the cell. uses ATP to provide energy to move membrane to form vesices to contain substances as it enters cell

40
Q

types of bulk transport

A

endocytosis
exocytosis
pinocytosis
phagocytosis

41
Q

what is exocytosis

A

the exit of substances from the cell after being transported through the cytoplasm in a vesicle
- digestive enzymes are often excreted this way

42
Q

what is endocytosis

A
  • bulk movement of materials into the cell
  • membrane engulfs the material
  • membrane fuses together
  • vesicle is formed
  • ATP required
43
Q

what are types of endoyctosis

A

phagocytosis and pinocytosis

44
Q

what is pinocytosis

A

the entry of liquid by some mechanism as phagocytosis excpet that the vesicles are smaller

45
Q

what is phagocytosis

A

the process by which the cell obtains solid materials that are too large to enter by diffusion or active transport
- a lysosome fuses with the vesicle formed, enzymes digest the soild material and the products are absorbed by the cytoplasm

46
Q

what are the steps of phagocytosis

A
  1. cell surface receptors bind to antigen on bacterium
  2. the cell membrane invaginates and the bacterium is taken into a phagosome by endocytosis
  3. lysosomes fuses with the phagosome and secrete digestive enzyes into it. the bacterium is digested
    4.products of digestion are absorbed into the cytoplasm
47
Q

what is co-transport

A
  • type of facilitated diffusion
  • brings molecules and ions into cells together on the same transport molecules/transports 2 substances in the same directionn
48
Q

what is osmosis

A

the movement of water molecules from an area od high water potential to an area of low water potential down a water potential gradient, across a partially permeable membrane

49
Q

what is water potential

A

the tendency for water molecules to enter or leave a solution by osmosis. water can move more freely in a dilute solution compared to a more concentrated one

50
Q

by adding solutes to pure water does it make the water potential higher or lower

51
Q

what is the water potential symbol

A

water fork thing

52
Q

what is water potential measured in

A

kilopascals (kPa)

53
Q

if the water potential number is less negative (pure water), is the water potential high or low

54
Q

if the water potential number is more negative (salty/sugary water), is the water potential high or low

55
Q

what are 3 types of solutions

A

hypertonic, isotonic, hypotonic

56
Q

what is hypertonic

A

have a lower water potential than the cell cytoplasm. it contains more solutes

57
Q

what is isotonic

A

have the same water potential as the cell cytoplasm. it contains the same conc of solutes

58
Q

what is hypotonic

A

has a high water potential than in the cell cytoplasm. it contains less solutes

59
Q

what does solute + solvent =

A

solution
eg sugar + water = sugary water

60
Q

how does osmosis of hypotonic, isotonic and hypertonic effect animal cells

A

hypotonic- shows lysis
isotonic- is normal
hypertonic- is crenated

61
Q

what is the water potential equation

A

water potential = solute potential + pressure potential

62
Q

what is the solute potential

A

conc of dissolved solute in the cell vacuole

63
Q

how the water potential equation is explained in plant cell

A

when water enters the cytoplasm and the vacole of a plant cell via osmosis, a hydrostatic pressure is set up and the contents push ouwards on the cell wall. as this pressure builds the cell wall develops an oppsoing force called the pressure potential (usually posistive)

64
Q

how does osmosis of hypotonic, isotonic and hypertonic effect plant cells

A

hypotonic- cell expands to full turgar
isotonic- cell shows incipient plasmolysis (cell memebrane just begins to move away from cell wall)
hypertonic- cell is plasmolysed

65
Q

effect of pure water on animal vs plant cells

A

both- water moves in by osmosis down a water potential gradient
a- cell burts open ( its haemolysed)
p- cell wall prevents bursting. membrane pushes against the wall (cell turgid)

66
Q

effect of concentrated sugar solution of animal vs plant cells

A

both- water moves out of cell by osmosis down a water potential gradient
a- cell shrinks and appear wrinkled (crenated)
p- cell membrane pulls away fromcell wall as water leaves (cell is plasmolysed)

67
Q

characteristics of a channel protein

A
  • pore
  • larger molecules
  • no ATP used
  • intrinsic (transmembrane)
68
Q

characteristics of carrier proteins

A
  • active transport
  • ATP
  • carrier molecule from a low to high conc and polar molecule
  • changed shape to allow molecule to get through
69
Q

whats the function of glycoproteins

A

cell to cell transport

biology- core components (8 decks)

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